In many industries, pipes or pipelines are utilized to transport fluid over distance. For example, in the oil and gas industry, there is a need to transport fluid over great distances, often over largely inaccessible terrain, in deep water, or in other subsea environments.
In the event of damage to a section of pipe, the importance of sealing the pipe in order to obviate or mitigate loss of fluid will be readily understood.
One repair option involves installing a repair clamp on the pipe outer diameter. Traditionally, this may take the form of a split sleeve bolted clamp with compression flanges at either end to provide a seal to the pipe outer diameter. A taper lock grip may optionally be provided often using the same compression flanges.
As many subsea pipelines are of relatively large diameter and transport fluid at high pressure, repair clamps, such as described above, are typically large and heavy and involve materials and manufacturing processes which result in significant lead times.
Two traditional construction methods for the manufacture of repair clamps are ring forging and fabrication. Ring forging requires a very large billet of material, which typically requires significant machining. Both the materials sourcing and manufacture result in a significant lead time.
Fabricated clamps involve simpler manufacturing processes and may use more readily available materials such as plate and pipe. Nevertheless, fabricating a clamp involves large structural welds which must be capable of resisting the full separation load and maintaining the rigidity of the clamp. Large structural welds often result in a degree of distortion and require additional machining and post weld heat treatment processes to be carried out, such that fabricated clamps will also involve a significant lead time.
In addition, due to the inaccessibility of many subsea pipelines, remotely operated vehicles (ROV's) are required to deploy and operate the clamps. As such, consideration must be given during the design and manufacture of such clamps in order that they are suitable for ROV use. By way of example, when converting a split sleeve clamp for ROV operation, sacrificial bolt tensioners may be provided to operate the bolting, as a result of which a separate mechanism is required to lock in the bolt pre-tension and permit the hydraulic supply to be detached.